Copper-selenium alloys



Patented Apr. 21, 1936 PATENT OFFICE 2,038,138 COPPER-SELENIUM anno s Cyril Stanley Smith, Cheshire, Conn., assignor to The American Brass Company, Waterbury,

Conn, a corporation of Connecticut Application September 2, 1933, Serial No. 887,967

10 Claims.

My invention concerns a series of alloys oi copper distinguished by a remarkable ease of machining. The free cutting properties are achieved without great sacrifice of strength or ductility by additions of selenium to pure copper or to a number of copper base alloys containing other elements. In many cases the other elements oi. the sulphur family, i. e., sulphur and tellurium, can be used in combination with selenium.

In the drawing:

Fig. 1 shows a set of curves demonstrating the ease of drilling copper alloys containing selenium; and

Fig. 2 shows the drillability of copper selenium alloys plotted against selenium content.

One of the principal objects of the refining operation as applied to the production, of metal- 110 copper from the crude matte is to remove from the metal the elements of the sulphur family. Almost without exception these elements have been hitherto regarded as extremely harmful to the malleability and ductility of copperin both the hot and cold conditions, and for this reason have been rigorously excluded. n account of this long-held opinion as to their deleterious effects they have not been subject to careful study in recent years and their true influence on copper has remained unknown. In my researches I have found that none of these elements in reasonable amounts are harmful to the hot and cold working properties of copper and that they all render the metal particularly readily cut with edge tools and very suitable for the manufacture of parts on so-called automatic screw machines or by any customary machining operations.

Selenium may be added to copper alloys either with the cold furnace charge or it may be added to the molten alloy in the form of the element or as CuzSe which is soluble in molten copper to the extent of about 4 per cent. selenium. On account of the volatility of the element and the poisonous nature of its fumes the latter method is to be preferred. A eutectic is formed at a temperature of .about 1065 C. containing approximately 3 per cent. selenium. Beyond 4.0 per cent further additions of selenium cause the formation of drops of CuzSe which tend to float out of the alloy during melting or solidification. Small amounts of selenium form eutectic areas filling in the spaces around the primarycopper grains and the amount of eutectic increases with selenium additions. The eutectic of copper and curse is very similar in microscopic appearance to the copper-copper oxide eutectic so familiar to metallurgists, and has-even less effect on the hot working properties. The addition of other elements to binary. copper-selenium. alloys usually coarsens the particles of CuaSe in the eutectic but, except in some special cases which will be discussed later, does not otherwise modify the structure.

Contrary. to the general impression, I have found that it is possible to forge copper saturated with selenium and I have hot rolled alloys containing up to 1.5 per cent. selenium with no dlfiiculty whatever, even using the severe reductions in a rolling mill designed for the commercial rolling of copper wire bars. Alloys containing up to this amount, and larger amounts, of selenium may be cold rolled, drawn or fabricated in any manner involving either hot or cold working with no particular precautions.

The alloys may also be used in the cast condition without fabrication. As with any copper alloy, it is advisable to melt and cast with exclusion of oxygen or with the addition of a defabricated condition are characterized by ex tremely high machinability. As is well known, copper is one of the most diflicult metals to. machine, since its soft and tough character causes it to form long tumings which stick to the tool and absorb much power which appears as heat. The particles of Curse in my alloys not only prevent the formation of a long chip, which may foul the tool in certain types of machine operations, but they also lubricate the tool, prevent sticking and reduce to a minimum the power required for the cutting operation and the heat generated. At the same time the tool life is considerably increased and a superior surface finish on the work obtained.

Alloys of copper which are desired to have free cutting qualities are at present made by ad- J ditions of lead in amounts up to about 4 per cent., but this, while favorably affecting machinability, does so at the expense of reducing the ductility, limiting the amount that the alloys can be cold rolled and entirely preventing hot ules are elongated in the same manner as thepiece as a whole, and after considerable extension form long thin fibres. The fibrous structure of the alloys is marked after very extensive rolling and results in rather poor properties when the metal is tested transverselyto the direction of rolling, but an annealing or soaking operation enables the strings of selenide to break up into more or less rounded globules which have comparatively little effect on the ductility in any direction. Due to the lower ductility of the base metal, the poor transverse properties due to the long thin flbers of selenide are more marked in alloys containing other elements, for example, silicon, nickel or tin, in addition to the selenium than they are with pure copper-selenium alloys.

To show the erroneous nature of the common conception that selenium renders copper brittle, I have given in Table I the tensile properties and electrical conductivity of some copper-selenium alloys which were melted and cast in 3 in. diameter ingots and then hot rolled to in. and cold drawn to in. diameter, at which size the tests were made. The table also includes results oi. tests on the same alloys after annealing at 600 C. This temperature was not sufliciently high to spheroidize completely the Curse fibers, and higher ductility would have resulted had the annealing been more drastic. The amount of selenium in these tests was limited to 1.5 per cent., since preliminary tests showed this to be sufilcient for the purpose in view. However, selenium can be added in far larger amounts up to the limit of solubility, about 4 per cent., without destroying the ductility of copper.

aoaense show thenumber-of turns necessary for a drill 0.25 in. diameter to penetrate 0.25 in. into the metal under the load shown. For comparison, a leaded brass containing 3 per cent. lead ani 35 per cent. zinc was included in the tests :s shown by dotted curve A, together with pure copper as'shown by curve B.

It will be seen that the alloys containing as little as 0.1 per cent. selenium are much easier to drill than pure copper, and that successive additions up to 1.5 per cent. progressively increase the amount of metal removed at each turn of the drill, although the improvement is not proportionally as great above 0.5 per cent. selenium as below this. The alloys containing 0.5 per cent. selenium are about equal in behavior to the leaded brass, while with more selenium than this the alloys are superior.

An improvement in machinability is secured with any addition of selenium as shown in Fig. 2

but to secure a material improvement selenium should be added in amount from approximately 0.05 per cent. up to the limit of solubility which is approximately 4.0 per cent., but the preferred nickel are attractive on account of their white color and their resistance to tarnish and corro- In the case of copper-nickel alloys of high nickel content, for example '70 per cent. nickel, there is apparently formed a low melting point constituent or eutectic containing nickel and selenium which interferes seriously with the malleability of the alloys. The amount of nickel that can be tolerated without the formation of this brittle constituent can be increased by the addition of zinc, but alloys containing up to approxi- TABLE I Tensile properties and electrical conductivity of cold drawn and. annealed copperselenium alloys Cmnposition pement Yield point Tensile Elongation Conductivity Alloy No. 0.5% ext. strength in 1.4" I. A. O. 8.

Copper Selenium lbs./sq. in. lbs/sq. in. per cent. percent, 20 0.

Cold drawn 99. 990 50, 700 52, 100 21. 4 99. 7 99. 88 0. 110 200 53, 200 19. 3 98. 9 99. 71 0. 26 51, 600 53, 000 15. 7 98. 0 99. 37 0. 48 50,900 53, 600 15.7 97. 4 99. 02 1. 01 49, 900 53, 400 ll. 4 94. 4 98. 57 1. 44 52, 000 54, 200 10. 0 92. 0

Annealed 1 h mr at 800 C. 99. 990 8, 700 32, 500 60. 0 102. 1 99. 88 0. 11 8, 400 32, 800 57. 1 99. 0 99. 71 0. 26 8, 900 32, 500 55. 7 100. 1 99. 37 0. 48 8, 000 32. 800 52. 9 98. 8 99. 02 1.01 8, 500 33, 300 48. 6 95. 6 9s. 57 l. 44 10, 100 33, 200 42. l 94. 4

These alloys were hot rolled from 3 in. to 0.625 in., annealed and cold drawn to 0.5 in. in one pass. Gauge length of test pieces-0357 in. diameter.

To demonstrate the remarkable ease of machining the alloys, I have reproduced in Figure 1 the results of some crude drill tests. These curves mately 30 per cent. nickel and 1.0 per cent, selenium are malleable both hot and cold in the absence of zinc. Alloys of somewhat higher nickel content are malleable if the selenium content is reduced.

Additions of zinc to alloys containing copper, nickel and selenium improve the casting and fabricating properties, and the alloys containing in the range of 10 to 30 per cent. nickel with 0.1 to 10 per cent. zinc and 0.05 to 2.0 per cent. selenium These alloys were hot rolledirom 3 in. to 0.625

in., annealed and cold draw: to 0.5 in. in two.

passes. Gauge length of test pieces-0.357 in.

would be preferred for general use. I1 zinc is diameter.

added in excess of approximately per cent. it Although it does not seem possible to add commences to form a zinc se enide wh h s n selenium to the brasses of high zinc content, mpl tely soluble in the molten alloy and comselenium may be added to copper-zinc alloys conmcn 0 scglegate- H w v w Smaller taining up to or per cent. zinc and a great a u ts o nc th s d es ot appe a d the zinc improvement in machinability obtained.

10 selenide. if r ed. ppa e y e a s n solu- The group of alloys containing in addition to tion in the Curse inclusions or is associated with copper and selenium also silicon, or tin, or nickel, t forming d p inclusions Which do not or zinc, or a combination of copper and selenium S pa in the liquid State- Additions of tin in with tinor nickel and zinc were selected and amount Of approximately 1 P centalso studied as representing important groups of cop- 15 p ove th bfl y of the alleys of copper with per alloys at present finding application. Most nickel and selenium and increase the ammmt of these alloys as commercially produced contain nickel that could he P135911t Without embrlttle' also additional elements which serve to improve ment Occurringthe properties in various ways and new copper The almyshf a tin have found apph' alloys will undoubtedly be developed in the fu- 20 Fatmn since prehistoric times where a strong ture based on these or entirely new combination corrosion resisting alloy was required The of elements. Selenium may be added to any comamount of tin is usually not g {1 -3 cent plex copper. alloys with as much facility as to :here g i are to 8 g the binary alloys unless there is present a large 8 as g as per Gen n oys w c are amount of some element which combines with used in the cast condition Usually to Improve selenium and forms a selenide which is not soluthe casting qualities 0. small amount of phosm in th n um 11 wh mi 1 phorus, silicon or zinc is added to the alloys. I 1 e l g d i g m have found that selenium in appreciable amounts S y e an Des no rema n even y and up to 1.5 per cent. may be added to bronzes dismbuted t mug .out the casting Among containing appreciable amounts of tin and up to common elements which do not prevent the re- 18 per cent. and confers great machlnability withtehtmn of Selenium in the alloy 1 have found out rendering the alloys brittle. Alloys of copper he following: Fe, Sn, Sb, AH, P. Si. 1, while with tin and selenium with a suitable deoxidizer the elements Al, Mg, Ca, Zr, and Mn if present make satisfactory sand castings. Chill castings, in more than a small quantity tend to eliminate die: castings, or permanent mold castings, can the selenium, while zinc if present in more. than also be made from the alloys containing selenium. perhaps 15 per cent. has a similar efiect. In the Copper alloys with silicon in all proporti n, case of manganese, amounts up to 0.5 per cent. but.there is useful ductility only in the range up are pemussime, although o per cent causes to approximately 5 per centsumo!" These alloys segregation of selenium. For all those elements 40 h51demb1e application m industry usually which combine with selenium more avidly than 1n combination with some other element to imdoes copper, there will be a limiting concentrw prove the strength or otherwise modify the tion below which the insoluble selenide will not erfles' I have studied alloys of copper contain form and the selenium will remain distributed ifi mgg z ggfg fi zg gg' f g n gxg uniformlythroughout the alloy, but above which have found the properties to be as shown in Table 32331 532 the selenide is insoluble m the v I f,fi g fi ;gg ggfi fi ifiifig i 'Although I have disclosed herein the addition 0.25 in. drill to penetrate 0.25 in. into the alloy selemum and a few i under a load of 86 pounds. The addition of it is at once obvious that the addition may be selenium m'b seen t increase t machjnmade to any alloys of copper with the disclosed ability and to have comparatively small effect or o h r elements, singly combined n any on the strength and ductility. manner, providing there is not an excessive TABLEII Tensile properties and machinability of cold drawn and annealed copper-silicon alloys containing selenium composition permnt Yield point Tensile strength ti Reduction 01 Machin- Alloy N0- smeon selenium g lbs/sq. in. areapercent ability index Cold irawn a. 0 0 55,800 111,850 a v 10. 4 50.0 020 Annealed 1 hour at 750 0'.

Number of turns 0! 0.25 in. drill necessary to penetrate 0.25 in. under load oi pounds.

amount of selenide formed that is insoluble in the liquid alloy and that is suillciently diflerent in density to be rapidly eliminated from the molten alloys. As examples of complex alloys I have made and used those containing copper with silicon, tin and selenium: copper with silicon,

iron, zinc and selenium; copper with nickel, zinc.

and selenium; copper with'nickel, zinc, tin and selenium; copper with tin, zinc and selenium. It is obvious, however, that there is almost no limit to the alloys of copper which can be made and to which selenium is a helpful addition when free-cutting qualities are desired. My invention covers the addition of selenium either as the element, copper-selenide or any other form to relatively pure copper or to any alloys of copper from which the selenium is not eliminated during casting.

Some of the alloys with selenium which are of importance include the following:

An alloy containing selenium from 0.05 to 4.0 per cent. the balance being substantially copper.

An aloy containing selenium approximately 1.0 per cent. and copper approximately 99.0 per cent.

An alloy consisting of approximately 0.5 per cent. selenium and 99.5 per cent. copper.

- Alloys containing from 0.05 per cent. to 4.0 per cent. selenium, the balance being principally copper with additions of one or more of the following: to per cent. silicon, 0 to 20 per cent. zinc, 0 to 50 per cent. nickel, 0 to 5 per cent. iron, 0 to 15 per cent. tin, 0 to 2 per cent. cadmium.

An alloy containing 0 to 5 per cent. silicon, 0.05 to 2 per cent. selenium, and 93 to 99.5 per cent. copper.

An alloy containing approximately 4.0 per cent. silicon, approximately 1.0 per cent. selenium, and approximately 95.0 per cent. copper.

Alloys containing 0 to 5 per cent. Si, 0 to 11 per cent. Fe, 0 to per cent..Zn, 0.05 to 2 per cent. Se, and the balance being principally copper.

An alloy containing approximately 3.5 per cent. si, 2 per cent. Fe, 2 per cent. Zn, 1 per cent. Se, the balance being principally copper.

Alloys containing 0 to 5 per cent. Si, 0 to 10 per cent. Sn, 0.05 to 2 per cent. Be. the balance being principally copper.

An alloy containing approximately 1.75 per cent. Si, 1.0 per cent. Sn, 1.0 per cent. Be, the balance being principallycopper.

Alloys containing 0 to 30 per cent. Ni, 0.05 to 2 per cent. Se, and the balance being principally copper.

An alloy containing approximately 20.0 per cent. Ni, 1.0 per cent. Se, the balance being principally copper.

Alloys containing 0 to 50 per cent. Ni, 0 to per cent. Zn, 0.05 to 2.0 per cent. Se, the balance being principally copper.

An alloy containing approximately per cent. Ni, 5 per cent. Zn, 1.0 per cent. Se, the balance being principally copper.

Alloys containing 0 to 15 per cent. Sn, 0.05 per cent. to 2.0 per cent, Se, the balance being principally copper. I

An alloy containing approximately 5.0 per cent. Sn, 1.0 per cent. Se, the balance being principally copper.

An alloy containing approximately 5.0 per cent. Sn, 1.0 per cent. Zn, 1.0 per cent. Se, the balance being principally copper.

Alloys containing 0 to 20 per cent. Zn, 0.05 to 2.0 per cent. Be, the balance being principally copper.

An alloy containing approximately 10 percent. Zn, 1 per cent. Se, the balance being principally copper.

Alloys containing 0 to 50 per cent, nickel, 0 to 4 per cent. tin, 0.05 to 2.0 per cent. selenium, the balance being principally copper.

An alloy containing approximately per cent. nickel, 1.0 per cent. tin, 1.0 per cent, selenium, the balance being principally copper.

Alloys containing 0 to 5 per cent. silicon, 0 to 10 per cent. zinc, 0 to 5 per cent. tin, 0.05 to 2.0 per cent. selenium, the balance being principally copper.

An alloy containing approximately 3.25 per cent. silicon, 1.5 per cent. zinc, 0.5 per cent. tin, 1.0 per cent. selenium, the balance being principally copper.

The other elements or the sulphur family, viz., sulphur and tellurium, behave in a manner similar to selenium. It may prove advisable to use additions of two or more or these elements simultaneously and it should be understood that whenever selenium is mentioned in this specification, selenium with more or less oi. the elements sulphur or tellurium, or sulphur and tellurium may be included. 1

It is possible to add selenium or a suitable selenide to alloys made by the process of compressing powders and sintering at a temperature below the melting point. In this case there is no limit to the alloys with which selenium can be combined, tor the lack of solubility in the liquid state is or no importance.

The lubricating nature of the copper selenide as shown by its action on the cutting tool suggests that the alloys containing selenides would be usein] for bearing purposes.

Having thus set forth the nature of my invention, what I claim is:

1. An alloy containing selenium from 0.1 per cent. to 4.0 per cent., the balance being copper.

2. An alloy containing from approximately 0.25 per cent. to 1.0 per cent. selenium, the balance being copper.

3. An alloy containing selenium approximately 1&0 per cent. and copper approximately 99.0 per cen '4. An alloy consisting of approximately 0.5 per cent. selenium, and approximately 99.5 per cent. copper.

5. A substantially zinc free copper base alloy which is characterized by ease of machining and which is workable by hot or cold rolling containing selenium in amount from 0.1 per cent. to 4.0 per cent.

6. A substantially zinc iree copper base alloy which is characterized by ease of machining and which is workable by hot or cold rolling contain- I over 15 per cent. zinc which is characterized by ease of machining and which is workable by hot or cold rolling containing selenium in amount from approximately 0.25 per cent. to approxi- 5 mately 1.0 per cent. a

10. A copper base alloy other than a brass of over 15 per cent. zinc which is characterized by ease of machining and which is workable by hot or cold rolling containing approximately 0.5 per cent. selenium. 

